1. Field of Invention
The present invention relates to a device in which a switching operation is made possible by means of an electric-field and a light or by means of an electric-field and, more particularly, to an organic electric-field switching device which can be easily transformed into a solid state device and has a neuro-information processing function of a multi-inputs/single output.
2. Description of the Related Art
Conventionally, a field-effect transistor made of a conductive polymer material has been employed as a device for switching by changing the conductivity between a source electrode and a drain electrode to an organic membrane by means of doping of a gas or an ion. In the above conventional way, the doping is achieved by an electrochemical method in which an electrolyte solution or a solid-state electrolyte is used, or by a method in which gas is diffused in an oxidizing gas ambient atmosphere. In the conductive polymer material, when the amount of a dopant adds in a few percent from zero, the conductivity characteristic changes dramatically, therefore, the manufacturing of the electric-field switching device can be realized by controlling the amount or the dopant by means of the electric-field.
FIG. 9 is a schematic diagram of the conventional organic electric-field switching device which utilizes a method of carriers' electric-field injection into the conductive polymer material, the method of which was disclosed by Elizabeth W. Faul, Antonio J. Rico, and Mark S. Wrighton, et al. "J. Physical Chemistry." 1985, vol. 89, p.1441.
In FIG. 9, a source electrode 2 and a drain electrode 3 are formed on a substrate and these electrodes and the substrate are disposed in a container 10. These electrodes are covered with a poly-aniline membrane 1 made of a conductive material. The container 10 is filled with sodium hydrogensulfate electrolyte solution 4. A reference electrode 5 containing electrolyte solution therein, the source electrode 2 and the drain electrode 3 are immersed in the sodium hydrogensulfate solution 4.
A description of an operation of the device will be given below. When a positive gate-voltage (0 to 0.3 V) is biased on the poly-aniline membrane, through the reference electrode 5 and sodium-hydrogensulfate electrolyte solution 4, conductivity is changed due to electrochemical oxidation of the poly-aniline membrane 1. When the voltage between the source electrode 2 and the drain electrode 3 is gradually swept during the oxidation (0 to 200 mV, 10 mV/sec), a characteristic of a field-effect transistor and the like can be obtained between a drain current, which flows between these electrodes 2 and 3, and the gate voltage.
As the conventional organic electric-field switching device has the foregoing construction, it is difficult to transform this device into a solid-state device because the electrolyte solution 4 or the reference electrode 5, which contains electrolyte solution therein, must be employed when the doping of the carrier is carried out by an electrochemical oxidation-and-reduction of the conductive polymer material for enabling switching by utilizing to the utmost the variation in conductivity. In addition, there has been a problem in that it is difficult to enable doping to be performed selectively in a plurality of predetermined areas of the conductive polymer materials by using a plurality of the reference electrodes 5 with the result that the multi-inputs cannot be converted into a single output because the reference electrode 5 biases the same level of the voltage on all of the electrolyte solution 4.